ANDROID: GKI: Add rockpi4 fragment and build.config

Add support for the Rock Pi 4 board downstream of GKI. This removes a
bitrotting custom defconfig and replaces it with a fragment based on
the GKI. Add the build.config for build automation purposes.

This configuration is not yet GKI compatible. Some options must be set
that are not GKI compliant:

CONFIG_ARCH_ROCKCHIP=y
CONFIG_COMMON_CLK_ROCKCHIP=y
CONFIG_DEVTMPFS=y
CONFIG_ROCKCHIP_GRF=y
CONFIG_ROCKCHIP_IOMMU=y
CONFIG_ROCKCHIP_MBOX=y
CONFIG_ROCKCHIP_PM_DOMAINS=y
CONFIG_ROCKCHIP_TIMER=y

Bug: 183963484
Change-Id: Id7376d6d377f453a3fe2c215d10d0424550de1bc
Signed-off-by: Alistair Delva <adelva@google.com>

build.config.rockpi4

@@ -0,0 +1,18 @@
+. ${ROOT_DIR}/${KERNEL_DIR}/build.config.common
+. ${ROOT_DIR}/${KERNEL_DIR}/build.config.aarch64
+TRIM_NONLISTED_KMI=""
+KMI_SYMBOL_LIST_STRICT_MODE=""
+
+BUILD_INITRAMFS=1
+DEFCONFIG=rockpi4_gki_defconfig
+FRAGMENT_CONFIG=${KERNEL_DIR}/arch/arm64/configs/rockpi4_gki.fragment
+PRE_DEFCONFIG_CMDS="KCONFIG_CONFIG=${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/${DEFCONFIG} ${ROOT_DIR}/${KERNEL_DIR}/scripts/kconfig/merge_config.sh -m -r ${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/gki_defconfig ${ROOT_DIR}/${FRAGMENT_CONFIG}"
+POST_DEFCONFIG_CMDS="rm ${ROOT_DIR}/${KERNEL_DIR}/arch/arm64/configs/${DEFCONFIG}"
+
+MAKE_GOALS="${MAKE_GOALS}
+rockchip/rk3399-rock-pi-4b.dtb
+"
+
+FILES="${FILES}
+arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4b.dtb
+"